Freedom of speech and unfettered access to information make countries stronger and are a universal "birthright", United States First Lady Michelle Obama yesterday told students in Beijing.

"When it comes to expressing yourself freely, and worshipping as you choose, and having open access to information, we believe those are universal rights that are the birthright of every person on this planet," she told an audience of about 200 Chinese and American students.

She was speaking at the Stanford Centre in Peking University on the third day of her week-long official visit to China with her mother and two daughters.

Countries are "stronger and more prosperous" when the voices and opinions of all their citizens can be heard, she said, according to a White House transcript.

In a "soft" diplomatic trip largely focused on education and people-to-people diplomacy and somewhat overshadowed by the fashion choices of Mrs Obama and her equally stylish Chinese counterpart Peng Li-yuan, the speech was seen as the US First Lady's attempt to nudge Beijing towards loosening its tight grip on information, especially online.

Said Mrs Obama: "It is so important for information and ideas to flow freely over the Internet and through the media.

"My husband and I are on the receiving end of plenty of questioning and criticism from our media and our fellow citizens, and it's not always easy. But I wouldn't trade it for anything in the world."

While the US frequently criticises China's human rights record and lack of protection of freedom of speech, Mrs Obama stopped short of calling on China to offer its citizens greater freedom.

But she emphasised the importance of study abroad programmes and the stake both the US and China have in each other's success.

"When it comes to the defining challenges of our time - whether it's climate change or economic opportunity or the spread of nuclear weapons - these are shared challenges. And no one country can confront them alone," Mrs Obama said.

Study abroad programmes should not be seen just as educational opportunities but as a "vital part of America's foreign policy", she added. They should also not discriminate against students from modest backgrounds.

Mrs Obama also spoke about how interdependent the world is, with "all (having) a stake in each other's success". Cures discovered here in Beijing, for instance, could save lives in the US while clean energy technologies from Silicon Valley in California could improve the environment in China, she said.

The US First Lady also visited the Summer Palace, where US schoolchildren studying Chinese performed for her.

She met US Embassy staff and their families later in the day. Over the next few days, she will travel to Xi'an and Chengdu.

Mrs Obama added a personal touch during a classroom session she attended, where students from China engaged with US students through video conferencing.

Speaking about how it was important that the young did not let fear guide them, she said: "My husband dragged me kicking and screaming into things I wanted no part of."

But more emphasis on learning foreign languages in the US was also necessary as too few students had exposure to other languages, she said, according to a White House pool report.

US President Barack Obama, for instance, regrets not having learnt another language, she said, adding that it is "not anti-American" to do so.

While online chatter about Mrs Obama's wardrobe continues, the fashion showdown between her and Madam Peng has died down since the Chinese leader's wife left on an official 11-day trip to Europe with President Xi Jinping yesterday.